Comparison of phenytoin serum concentrations in premature neonates following intravenous and oral administration

OBJECTIVE: To compare the serum concentrations attained following intravenous and oral administration of phenytoin in premature neonates. DESIGN: A prospective, uncontrolled study was conducted over 6 years. Phenhydan concentrate for infusion (Desitin, Hamburg, Germany) was used for intravenous infusion, and Epanutin suspension (Parke-Davis, Freiburg, Germany) was used for oral therapy. Blood samples were analyzed by using a fluorescence polarization immunoassay analyzer TDx model by Abbott Laboratories. SETTING: A university-affiliated district hospital. PARTICIPANTS: Twenty premature neonates who were administered intravenous and/or oral phenytoin between February 1991 and February 1997. MAIN OUTCOME MEASURES: Serum phenytoin concentrations on intravenous and oral phenytoin. RESULTS: Nine patients received intravenous (group A) and 15 patients received oral (group B) therapy. Mean +/- SD postnatal age (41 +/- 8.7 vs. 48 +/- 17 d; p = 0.03) and actual body weight (1.56 +/- 0.38 vs. 1.88 +/- 0.75 kg; p = 0.02) were slightly higher in group B. There were no significant differences between the groups in mean +/- SD gestational age (26.1 +/- 1.37 vs. 26.9 +/- 3.30 wk), 5-minute Apgar score (8.7 +/- 1.11 vs. 7.7 +/- 2.26), daily dosage (8.1 +/- 3.86 vs. 8.1 +/- 4.21 mg/kg/d), and phenytoin serum concentration (8.7 +/- 7.36 vs. 9.6 +/- 5.83 micrograms/mL). CONCLUSIONS: Contrary to data in the current literature, reliable serum concentrations in premature neonates were achieved by oral administration of phenytoin suspension. Oral therapy offers a number of advantages and considerably reduces the cost of therapy. Due to substantial variations in phenytoin pharmacokinetics in neonates, close monitoring of serum concentrations is required. Further investigation is required to confirm these results, especially in neonates younger than 20 days' postnatal age and those receiving products other than Epanutin.